#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int swap(int a)
{
    if (a == 0 || a == 1) return 1;
    else return swap(a - 1) + swap(a - 2);
}


int main() {
    int a = 0;
    scanf("%d", &a);
    printf("%d", swap(a));

    return 0;
}